Modern day shipbuilding techniques generally consist of pre-fabricated block hull construction, where multi-deck segments of the hull or ship superstructure are built in designated locations of a shipyard and then transported by large transporter and installed by heavy-duty cranes to be welded together. This method is known as block construction.
In block construction, large segments of the ship constructed of steel structural plates are assembled and outfitted with equipment, electrical, and utilities into building blocks called modules. These massive modules are then moved or lifted and joined together in what is known as the ship assembly area. This system turns out to be more efficient than assembling the whole structural shape first followed by outfitting with equipment, electrical, and utilities later. The open modules save man-hours by allowing easier access to the conduit for utilities and space for the equipment.
In conventional shipbuilding, ships are built in an upright position supported by chocks to support the irregular shapes of the ships during construction in the dry dock. Plate assemblies, including stiffeners for either the external form or internal bulkheads are built in automated plate shops. These plate shops are equipped with automated cutting, fitting, and welding equipment. The plate assemblies are built to the largest size that can be transported and lifted into place to form the interior of the ship's structure. Plate assemblies are moved on specially designed hydraulic actuated carriers in the largest sizes possible to the ship assembly area. Plate assemblies are lifted by large overhead cranes to be fitted and welded into the modules being assembled.
As girders, decks, beams, and bulkheads are positioned and welded into place, holes for utilities are cut and installed, or, if they were cut in prefab, holes are aligned. Conduits are placed and affixed to the plates and utilities are run during or after construction of the module.
Next the hull exterior is lifted into place with cranes on chocks and welded together. Interior bulkheads are welded to the external shells to complete the ship's structure. For streamlined ships, the plates must be lifted into place and held on the underside of the hull and then welded. As the modules are completed, they are then transported out to the ship assembly area on massive transporters.
As plate assemblies are positioned and welded into place, holes for utilities are cut or aligned. Conduits are then placed and affixed to the plates. Utilities and product piping are run during or after construction of the module. Utilities must be made watertight during this process.
While block construction results in numerous improvements over the older piecemeal methods of naval architecture and shipbuilding, it too has drawbacks. Conventional ship hulls are assembled using flat plates stiffened with structural shapes as plate subassemblies. The exterior of the ships as well as internal bulkheads use this basic building design. The entire ship must be designed and detailed to address all the stresses induced from its operations in all sea states. In a typical ship, there are thousands of individual plates to be designed as part of the overall plate subassemblies. Not only do current shipbuilding practices cause complex penetration and stress issues for utilities, but the individual shapes of plates must be cut and assembled to form the ship structure, which is a time consuming process. Additionally, block modules weigh thousands of tons and require large transporters and cranes.
A need exists for a new ship design that reduces the engineering design, detailing, and fabrication complexities required in conventional shipbuilding as well as improves the stress profile of a ship.